As computer systems grow in speed and shrink in size, power consumed within the computer per unit volume (power density) increases drastically. Thus, it becomes evermore important to dissipate the heat generated by components within the computer during their operation to ensure that the components remain within their normal operating temperature ranges to prevent the components from failing immediately or from having too short a lifetime.
In very early desktop personal computers, components were passively cooled by radiation or convection, the surfaces of the components themselves interfacing directly with still or convecting air surrounding the component to transfer heat thereto. Unfortunately, air is not a particularly good conductor of heat. In these early desktop computers, if the heated air had nowhere to go, it clung to the component, acting as a thermal insulator of sorts and increasing operating temperatures. Eventually computers were provided with fans to actively move air over the surfaces of the components, increasing temperature differential between the surfaces of the components and the surrounding air to increase efficiency of heat transfer. The increased temperature differential overcame some of the poor heat conductor qualities of air.
In portable computers (and, in particular, notebook computers), the problem of heat dissipation is even more pronounced, due in principal part to the confines of the size of such computers. Even though such computers make use of low power complementary metal oxide semiconductor ("CMOS") components (to conserve battery power) that dissipate somewhat less heat than higher power components, these CMOS components are nonetheless placed close together, exacerbating the problem of dissipating heat.
Of all components in a portable computer, the microprocessor central processing unit ("CPU") generates the most heat during operation of the computer. This is a result of its role as the electrical center of attention in the computer. Thus, in prior art portable computers, the CPU was placed close to the outer case to allow the outer case to transfer heat from the CPU to the environment outside the computer.
As new generations of microprocessors have arrived, however, this relatively simple scheme has become decidedly inadequate, risking destruction of the CPU by overheating. Due to power, space and circulation limitations inherent in portable computers (as opposed to desktop computers), it is impractical to fan-cool the components.
Some portable computers provide an access door proximate the CPU to allow external access to the CPU by a user or technician for purposes of conveniently testing or upgrading the CPU during the life of the computer. In these computers, the door is typically composed of plastic of same or similar type as the remainder of the outer case. An interior surface of the door is separated a small distance from the component for clearance purposes. Thus, heat transfer takes place from the component, through the air separating the component from the door, through the door and into the environment.
What is needed in the art is a more effective way of cooling the microprocessor or other heat-producing components in a portable computer. It is important that external access to the microprocessor not be compromised.